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<a name="Characters-implementation"></a>
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<a name="Characters"></a>
<h3 class="section">4.4 Characters</h3>

<ul>
<li> <cite>The number of bits in a byte (C90 3.4, C99 and C11 3.6).</cite>

<p>Determined by ABI.
</p>
</li><li> <cite>The values of the members of the execution character set (C90,
C99 and C11 5.2.1).</cite>

<p>Determined by ABI.
</p>
</li><li> <cite>The unique value of the member of the execution character set produced
for each of the standard alphabetic escape sequences (C90, C99 and C11
5.2.2).</cite>

<p>Determined by ABI.
</p>
</li><li> <cite>The value of a <code>char</code> object into which has been stored any
character other than a member of the basic execution character set
(C90 6.1.2.5, C99 and C11 6.2.5).</cite>

<p>Determined by ABI.
</p>
</li><li> <cite>Which of <code>signed char</code> or <code>unsigned char</code> has the same
range, representation, and behavior as &ldquo;plain&rdquo; <code>char</code> (C90
6.1.2.5, C90 6.2.1.1, C99 and C11 6.2.5, C99 and C11 6.3.1.1).</cite>

<a name="index-fsigned_002dchar-1"></a>
<a name="index-funsigned_002dchar-1"></a>
<p>Determined by ABI.  The options <samp>-funsigned-char</samp> and
<samp>-fsigned-char</samp> change the default.  See <a href="C-Dialect-Options.html#C-Dialect-Options">Options Controlling C Dialect</a>.
</p>
</li><li> <cite>The mapping of members of the source character set (in character
constants and string literals) to members of the execution character
set (C90 6.1.3.4, C99 and C11 6.4.4.4, C90, C99 and C11 5.1.1.2).</cite>

<p>Determined by ABI.
</p>
</li><li> <cite>The value of an integer character constant containing more than one
character or containing a character or escape sequence that does not map
to a single-byte execution character (C90 6.1.3.4, C99 and C11 6.4.4.4).</cite>

<p>See <a href="http://gcc.gnu.org/onlinedocs/cpp/Implementation_002ddefined-behavior.html#Implementation_002ddefined-behavior">Implementation-defined
behavior</a> in <cite>The C Preprocessor</cite>.
</p>
</li><li> <cite>The value of a wide character constant containing more than one
multibyte character or a single multibyte character that maps to
multiple members of the extended execution character set, or
containing a multibyte character or escape sequence not represented in
the extended execution character set (C90 6.1.3.4, C99 and C11
6.4.4.4).</cite>

<p>See <a href="http://gcc.gnu.org/onlinedocs/cpp/Implementation_002ddefined-behavior.html#Implementation_002ddefined-behavior">Implementation-defined
behavior</a> in <cite>The C Preprocessor</cite>.
</p>
</li><li> <cite>The current locale used to convert a wide character constant consisting
of a single multibyte character that maps to a member of the extended
execution character set into a corresponding wide character code (C90
6.1.3.4, C99 and C11 6.4.4.4).</cite>

<p>See <a href="http://gcc.gnu.org/onlinedocs/cpp/Implementation_002ddefined-behavior.html#Implementation_002ddefined-behavior">Implementation-defined
behavior</a> in <cite>The C Preprocessor</cite>.
</p>
</li><li> <cite>Whether differently-prefixed wide string literal tokens can be
concatenated and, if so, the treatment of the resulting multibyte
character sequence (C11 6.4.5).</cite>

<p>Such tokens may not be concatenated.
</p>
</li><li> <cite>The current locale used to convert a wide string literal into
corresponding wide character codes (C90 6.1.4, C99 and C11 6.4.5).</cite>

<p>See <a href="http://gcc.gnu.org/onlinedocs/cpp/Implementation_002ddefined-behavior.html#Implementation_002ddefined-behavior">Implementation-defined
behavior</a> in <cite>The C Preprocessor</cite>.
</p>
</li><li> <cite>The value of a string literal containing a multibyte character or escape
sequence not represented in the execution character set (C90 6.1.4,
C99 and C11 6.4.5).</cite>

<p>See <a href="http://gcc.gnu.org/onlinedocs/cpp/Implementation_002ddefined-behavior.html#Implementation_002ddefined-behavior">Implementation-defined
behavior</a> in <cite>The C Preprocessor</cite>.
</p>
</li><li> <cite>The encoding of any of <code>wchar_t</code>, <code>char16_t</code>, and
<code>char32_t</code> where the corresponding standard encoding macro
(<code>__STDC_ISO_10646__</code>, <code>__STDC_UTF_16__</code>, or
<code>__STDC_UTF_32__</code>) is not defined (C11 6.10.8.2).</cite>

<p>See <a href="http://gcc.gnu.org/onlinedocs/cpp/Implementation_002ddefined-behavior.html#Implementation_002ddefined-behavior">Implementation-defined
behavior</a> in <cite>The C Preprocessor</cite>.  <code>char16_t</code> and
<code>char32_t</code> literals are always encoded in UTF-16 and UTF-32
respectively.
</p>
</li></ul>

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